Effect of Additional Dry Heat Curing on Microflexural Strength in Three Types of Resin Composite: An In Vitro Study

Abstract

Aim: Additional dry heat curing is a method that favorably influences the mechanical properties of an indirect resin composite restoration. Microflexural strength is a property currently applied for the evaluation of indirect resin composite restorations. The aim of the present study was to assess the effect of additional dry heat curing on microflexural strength in three types of direct-use resin composites. Materials and Methods: This in vitro study consisted of 70 resin composites samples made with a 6 × 2 × 1 mm metal matrix and divided into seven experimental groups, which included Gr1a: Tetric N-Ceram without additional dry heat curing (n = 10); Gr1b: Tetric N-Ceram with additional dry heat curing (n = 10); Gr 2a: Filtek Z350 XT without additional dry heat curing (n = 10); Gr2b: Filtek Z350 XT with additional dry heat curing (n = 10); Gr3a: Filtek Z250 without additional dry heat curing (n = 10); Gr3b: Filtek Z250 with additional dry heat curing (n = 10); and Gr4: SR Nexco Paste (control) without additional dry heat curing (n = 10). The samples were stored in distilled water at 37 °C for 24 h. A universal testing machine with a 2000 N load cell at a speed of 1 mm/min was used to assess flexural strength. The data were analyzed with a parametric ANOVA test with Tukey’s post hoc intergroup factor (for groups without heat treatment) and a nonparametric Kruskall Wallis test with Bonferroni’s post hoc (for groups with heat treatment). In addition, the comparison of independent groups in each resin composite type with and without heat treatment was performed with a Mann Whitney U test. A significance level of p < 0.05 was considered. Results: The Filtek Z250 resin composite with and without additional dry heat curing presented the highest microflexural strength values with 137.27 ± 24.43 MPa and 121.32 ± 9.74 MPa, respectively, while the SR Nexco Paste (control) resin composite presented the lowest microflexural strength values with 86.06 ± 14.34 MPa compared to all the resin composites with additional dry heat curing. The Filtek Z250 and Filtek Z350XT resin composites with and without additional dry heat curing presented significantly higher microflexural strength versus the SR Nexco (p < 0.05) and Tetric N-Ceram (p < 0.05) resin composites. In addition, the Filtek Z350XT and Tetric N-Ceram resin composites with additional dry heat curing showed significantly higher microflexural strength (p < 0.05) compared to those without additional dry heat curing. Conclusions: The Filtek Z250 and Z350XT resin composites had significantly higher microflexural strength values with and without additional dry heat curing. In addition, the Filtek Z350XT and Tetric N-Ceram resin composites subjected to additional dry heat curing showed significantly higher microflexural strength compared to when they did not receive the same procedure, a situation that did not occur with the Filtek Z250 resin composite.

Effect of Polywave and Monowave Light Curing Units on the Microtensile Bond Strength and Failure Types of Different Bulk-Fill Resin Composites: An in vitro Study

“…33 , 37 It is also important to consider the large shrinkage stresses that are generated within the resin composite and at the dentin-composite adhesive interface because they can affect the bond strength. 25 , 41 , 42 If the stress resulting from polymerization contraction exceeds the bond strength of the composite to the cavity walls, failures may occur at the marginal bonds. However, if the bonding interface resists and remains intact, residual stress could be transferred to adjacent tooth structures, possibly resulting in fractures of the enamel or dentin.…”

Trueness, Flexural Strength, and Surface Properties of Various Three-Dimensional (3D) Printed Interim Restorative Materials after Accelerated Aging

“…Further research is needed to better understand the effects of filler content and polymerization on the mechanical properties and surface roughness of 3D printed objects. Finally, microflexural testing is a more suitable option for testing dental restoration materials and has more clinical relevance because dental restorations are small [ 31 ].…”

In Vitro Evaluation of Candida albicans Adhesion on Heat-Cured Resin-Based Dental Composites

“…This is the reasons why, when dealing with indirect restorations, resin composites are conveniently subjected to further heat curing. Such an additional heat treatment leads to an increase in the degree of conversion and improved mechanical properties such as microhardness, flexural strength, fracture toughness, wear resistance, tensile strength, color stability and a reduction of wear [11][12][13][14]. Thus, it seemed of greater clinical interest to investigate the antimicrobial activity of materials when they are used in their best performing modes.…”

“…The degree of Materials 2023, 16, 5818 2 of 12 conversion of double carbon bonds to single carbon bonds achieved during polymerization directly affects the final characteristics of photo-cured composites [10]. When resin composites are used for indirect restorations, before final restoration delivery, they can be further processed in the dental laboratory; here, they are typically subjected to additional heat curing protocols that, according to several studies, allow for enhanced material's microhardness, flexural strength, fracture toughness, wear resistance, tensile strength and color stability [11][12][13][14]. The conversion of monomers into durable polymer chains is increased as a result of such a heat curing [15,16].…”